Methods for uplink multiuser signaling and transmission

ABSTRACT

A method implemented by an Access Point (AP) in a Wireless Local Area Network (WLAN) to initiate an uplink (UL) multi-user (MU) simultaneous transmission. The method includes generating a trigger frame that initiates the UL MU simultaneous transmission, where the trigger frame includes (1) a UL MU Physical Layer Convergence Protocol (PLCP) Protocol Data Unit (PPDU) attributes field to indicate attributes pertaining to a UL MU PPDU transmitted to the AP during the UL MU simultaneous transmission that are common to a plurality of stations (STAs) that are scheduled to participate in the UL MU simultaneous transmission and (2) a STA Physical Layer Service Data Unit (PSDU) attributes field for a particular STA from the plurality of STAs to indicate attributes pertaining to the UL MU PPDU that are specific to the particular STA. The method further includes transmitting the trigger frame through a wireless medium.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/145,732 filed Sep. 28, 2018, which is a continuation of U.S.application Ser. No. 15/171,870 filed Jun. 2, 2016 (now U.S. Pat. No.10,116,361 issued Oct. 30, 2018), which claims the benefit of U.S.Provisional Application No. 62/305,161 filed Mar. 8, 2016, U.S.Provisional Application No. 62/240,423 filed Oct. 12, 2015, U.S.Provisional Application No. 62/191,628 filed Jul. 13, 2015, and U.S.Provisional Application No. 62/170,012 filed Jun. 2, 2015, which arehereby incorporated by reference.

FIELD OF INVENTION

The embodiments are related to the field of Wireless Local Area Network(WLAN) operation. More specifically, the embodiments relate to a methodand apparatus for initiating an uplink (UL) multi-user (MU) simultaneoustransmission in a WLAN. Other embodiments are also disclosed.

BACKGROUND

Institute of Electrical and Electronics Engineers (IEEE) 802.11 is a setof physical and Media Access Control (MAC) specifications forimplementing wireless local area network (WLAN) communications. Thesespecifications provide the basis for wireless network products using theWi-Fi brand managed and defined by the Wi-Fi Alliance. Thespecifications define the use of the 2.400-2.500 GHz as well as the4.915-5.825 GHz bands. These spectrum bands are commonly referred to asthe 2.4 GHz and 5 GHz bands. Each spectrum is subdivided into channelswith a center frequency and bandwidth. The 2.4 GHz band is divided into14 channels spaced 5 MHz apart, though some countries regulate theavailability of these channels. The 5 GHz band is more heavily regulatedthan the 2.4 GHz band and the spacing of channels varies across thespectrum with a minimum of a 5 MHz spacing dependent on the regulationsof the respective country or territory.

WLAN devices are currently being deployed in diverse environments. Theseenvironments are characterized by the existence of many Access Points(APs) and non-AP stations (STAs) in geographically limited areas.Increased interference from neighboring devices gives rise toperformance degradation. Additionally, WLAN devices are increasinglyrequired to support a variety of applications such as video, cloudaccess, and offloading. Video traffic, in particular, is expected to bethe dominant type of traffic in WLAN deployments. With the real-timerequirements of some of these applications, WLAN users demand improvedperformance.

In a task group called Institute of Electrical and Electronics Engineers(IEEE) 802.11ax, High Efficiency WLAN (HEW) standardization is underdiscussion. The HEW aims at improving performance felt by usersdemanding high-capacity and high-rate services. The HEW may supportuplink (UL) multi-user (MU) simultaneous transmission, which includesuplink Multi-User Multiple-Input Multiple-Output (MU-MIMO) and uplinkOrthogonal Frequency Division Multiple Access (OFDMA) transmissions.

SUMMARY

The embodiments provide a method implemented by an Access Point (AP) ina Wireless Local Area Network (WLAN) to initiate an uplink (UL)multi-user (MU) simultaneous transmission. The method includesgenerating a trigger frame that initiates the UL MU simultaneoustransmission, where the trigger frame includes (1) a UL MU PhysicalLayer Convergence Protocol (PLCP) Protocol Data Unit (PPDU) attributesfield to indicate attributes pertaining to a UL MU PPDU transmitted tothe AP during the UL MU simultaneous transmission that are common to aplurality of stations (STAs) that are scheduled to participate in the ULMU simultaneous transmission and (2) a STA Physical Layer Service DataUnit (PSDU) attributes field for a particular STA from the plurality ofSTAs to indicate attributes pertaining to the UL MU PPDU that arespecific to the particular STA. The method further includes transmittingthe response frame to the unassociated STA through a wireless medium.

The embodiments provide a network device to function as an Access Point(AP) in a Wireless Local Area Network (WLAN) to initiate an uplink (UL)multi-user (MU) simultaneous transmission. The network device includes aRadio Frequency (RF) transceiver, a set of one or more processors, and anon-transitory machine-readable medium having stored therein a UL MUsimultaneous transmission module, which when executed by the set of oneor more processors, causes the network device to generate a triggerframe that initiates the UL MU simultaneous transmission, where thetrigger frame includes (1) a UL MU Physical Layer Convergence Protocol(PLCP) Protocol Data Unit (PPDU) attributes field to indicate attributespertaining to a UL MU PPDU transmitted to the AP during the UL MUsimultaneous transmission that are common to a plurality of STAs thatare scheduled to participate in the UL MU simultaneous transmission and(2) a STA Physical Layer Service Data Unit (PSDU) attributes field for aparticular STA from the plurality of STAs to indicate attributespertaining to the UL MU PPDU that are specific to the particular STA.The UL MU simultaneous transmission module, when executed by the networkdevice, further causes the network device to transmit the trigger framethrough a wireless medium.

The embodiments provide a non-transitory machine-readable storage mediumhaving computer code stored therein that is to be executed by a set ofone or more processors of a network device functioning as an AccessPoint (AP) in a Wireless Local Area Network (WLAN) to initiate an uplink(UL) multi-user (MU) simultaneous transmission. The computer code, whenexecuted by the network device, causes the network device to generate atrigger frame that initiates the UL MU simultaneous transmission, wherethe trigger frame includes (1) a UL MU Physical Layer ConvergenceProtocol (PLCP) Protocol Data Unit (PPDU) attributes field to indicateattributes pertaining to a UL MU PPDU transmitted to the AP during theUL MU simultaneous transmission that are common to a plurality of STAsthat are scheduled to participate in the UL MU simultaneous transmissionand (2) a STA Physical Layer Service Data Unit (PSDU) attributes fieldfor a particular STA from the plurality of STAs to indicate attributespertaining to the UL MU PPDU that are specific to the particular STA.The computer code, when executed by the network device, further causesthe network device to transmit the trigger frame through a wirelessmedium.

The embodiments provide a method implemented by a station (STA) in aWireless Local Area Network (WLAN) to participate in an uplink (UL)multi-user (MU) simultaneous transmission to an access point (AP) withone or more other STAs. The method includes receiving a trigger framethat initiates the UL MU simultaneous transmission from the AP, wherethe trigger frame includes (1) a UL MU Physical Layer ConvergenceProtocol (PLCP) Protocol Data Unit (PPDU) attributes field to indicateattributes pertaining to a UL MU PPDU transmitted to the AP during theUL MU simultaneous transmission that are common to the STA and the oneor more other STAs and (2) a STA Physical Layer Service Data Unit (PSDU)attributes field for the STA to indicate attributes pertaining to the ULMU PPDU that are specific to the STA. The method further includestransmitting the UL MU PPDU to the AP through a wireless medium duringthe UL MU simultaneous transmission, according to the attributespertaining to the UL MU PPDU indicated in the UL MU PPDU attributesfield and the STA PSDU attributes field for the STA.

The embodiments provide a network device to function as a station (STA)in a Wireless Local Area Network (WLAN) to participate in an uplink (UL)multi-user (MU) simultaneous transmission to an access point (AP) withone or more other STAs. The network device includes a Radio Frequency(RF) transceiver, a set of one or more processors, and a non-transitorymachine-readable medium having stored therein a UL MU simultaneoustransmission module, which when executed by the set of one or moreprocessors, causes the network device to receive a trigger frame thatinitiates the UL MU simultaneous transmission from the AP, where thetrigger frame includes (1) a UL MU Physical Layer Convergence Protocol(PLCP) Protocol Data Unit (PPDU) attributes field to indicate attributespertaining to a UL MU PPDU transmitted to the AP during the UL MUsimultaneous transmission that are common to the STA and the one or moreother STAs and (2) a STA Physical Layer Service Data Unit (PSDU)attributes field for the STA to indicate attributes pertaining to the ULMU PPDU that are specific to the STA. The UL MU simultaneoustransmission module, when executed by the network device, further causesthe network device to transmit the UL MU PPDU to the AP through awireless medium during the UL MU simultaneous transmission, according tothe attributes pertaining to the UL MU PPDU indicated in the UL MU PPDUattributes field and the STA PSDU attributes field for the STA.

The embodiments provide a non-transitory machine-readable storage mediumhaving computer code stored therein that is to be executed by a set ofone or more processors of a network device functioning as a station(STA) in a Wireless Local Area Network (WLAN) to participate in anuplink (UL) multi-user (MU) simultaneous transmission to an access point(AP) with one or more other STAs. The computer code, when executed bythe network device, causes the network device to receive a trigger framethat initiates the UL MU simultaneous transmission from the AP, wherethe trigger frame includes (1) a UL MU Physical Layer ConvergenceProtocol (PLCP) Protocol Data Unit (PPDU) attributes field to indicateattributes pertaining to a UL MU PPDU transmitted to the AP during theUL MU simultaneous transmission that are common to the STA and the oneor more other STAs and (2) a STA Physical Layer Service Data Unit (PSDU)attributes field for the STA to indicate attributes pertaining to the ULMU PPDU that are specific to the STA. The computer code, when executedby the network device, further causes the network device to transmit theUL MU PPDU to the AP through a wireless medium during the UL MUsimultaneous transmission, according to the attributes pertaining to theUL MU PPDU indicated in the UL MU PPDU attributes field and the STA PSDUattributes field for the STA.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are illustrated by way of example, and not by way oflimitation, in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that differentreferences to “an” or “one” embodiment in this specification are notnecessarily to the same embodiment, and such references mean at leastone. Further, when a particular feature, structure, or characteristic isdescribed in connection with an embodiment, it is submitted that it iswithin the knowledge of one skilled in the art to affect such feature,structure, or characteristic in connection with other embodimentswhether or not explicitly described.

FIG. 1 is a diagram illustrating operations of a UL MU simultaneoustransmission, according to some embodiments.

FIG. 2 is a diagram illustrating operations in a WLAN where a STA missesa beacon frame transmitted by an AP and thus is unaware of the starttime of trigger frame transmissions, according to some embodiments.

FIG. 3 is a diagram illustrating operations in a WLAN where even thougha STA misses a beacon frame transmitted by an AP, the STA becomes awareof the start time of trigger frame transmissions based on informationincluded in a trigger frame, according to some embodiments.

FIG. 4A is a diagram illustrating a format of a trigger frame, accordingto some embodiments.

FIG. 4B is a diagram illustrating a format of a common info field or ULMU PPDU attributes field, according to some embodiments.

FIG. 4C is a diagram illustrating a format of a per-user info field orSTA PSDU attributes field, according to some embodiments.

FIG. 5 is a flow diagram of a process implemented by a network devicefunctioning as an AP to initiate a UL MU simultaneous transmission,according to some embodiments.

FIG. 6 is a flow diagram of a process implemented by a network devicefunctioning as a STA to participate in a UL MU simultaneous transmissionto an AP with one or more other STAs, according to some embodiments.

FIG. 7 is a block diagram of a network device implementing a STA or APthat executes a random access process and module, according to someembodiments.

FIG. 8 is a block diagram of a WLAN, according to some embodiments.

FIG. 9 is a schematic block diagram exemplifying a transmitting signalprocessor in a WLAN device, according to some embodiments.

FIG. 10 is a schematic block diagram exemplifying a receiving signalprocessing unit in the WLAN, according to some embodiments.

FIG. 11 is a timing diagram providing an example of the Carrier SenseMultiple Access/Collision Avoidance (CSMA/CA) transmission procedure,according to some embodiments.

DETAILED DESCRIPTION

The embodiments disclosed herein provide a method and apparatus forinitiating an uplink (UL) multi-user (MU) simultaneous transmission in aWireless Local Area Network (WLAN). An embodiment is a methodimplemented by an access point (AP) that generates a trigger frame toinitiate a UL MU simultaneous transmission, where the trigger frameincludes a UL MU Physical Layer Convergence Protocol (PLCP) ProtocolData Unit (PPDU) attributes field to indicate attributes pertaining to aUL MU PPDU transmitted to the AP during the UL MU simultaneoustransmission that are common to a plurality of STAs that are scheduledto participate in the UL MU simultaneous transmission and a STA PhysicalLayer Service Data Unit (PSDU) attributes field for a particular STAfrom the plurality of STAs to indicate attributes pertaining to the ULMU PPDU that are specific to the particular STA. The AP then transmitsthe trigger frame through a wireless medium. Other embodiments are alsodescribed and claimed.

In the following description, numerous specific details are set forth.However, it is understood that embodiments may be practiced withoutthese specific details. In other instances, well-known circuits,structures and techniques have not been shown in detail in order not toobscure the understanding of this description. It will be appreciated,however, by one skilled in the art that embodiments may be practicedwithout such specific details. Those of ordinary skill in the art, withthe included descriptions, will be able to implement appropriatefunctionality without undue experimentation.

References in the specification to “one embodiment,” “an embodiment,”“an example embodiment,” etc., indicate that the embodiment describedmay include a particular feature, structure, or characteristic, butevery embodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to effect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

In the following description and claims, the terms “coupled” and“connected,” along with their derivatives, may be used. It should beunderstood that these terms are not intended as synonyms for each other.“Coupled” is used to indicate that two or more elements, which may ormay not be in direct physical or electrical contact with each other,co-operate or interact with each other. “Connected” is used to indicatethe establishment of communication between two or more elements that arecoupled with each other. A “set,” as used herein refers to any positivewhole number of items including one item.

An electronic device stores and transmits (internally and/or with otherelectronic devices over a network) code (which is composed of softwareinstructions and which is sometimes referred to as computer program codeor a computer program) and/or data using machine-readable media (alsocalled computer-readable media), such as non-transitory machine-readablemedia (e.g., machine-readable storage media such as magnetic disks,optical disks, read only memory, flash memory devices, phase changememory) and transitory machine-readable transmission media (also calleda carrier) (e.g., electrical, optical, radio, acoustical or other formof propagated signals—such as carrier waves, infrared signals). Thus, anelectronic device (e.g., a computer) includes hardware and software,such as a set of one or more processors coupled to one or morenon-transitory machine-readable storage media (to store code forexecution on the set of processors and data) and a set of one or morephysical network interface(s) to establish network connections (totransmit code and/or data using propagating signals). Put another way, atypical electronic device includes memory comprising non-volatile memory(containing code regardless of whether the electronic device is on oroff) and volatile memory (e.g., dynamic random access memory (DRAM),static random access memory (SRAM)), and while the electronic device isturned on that part of the code that is currently being executed iscopied from the slower non-volatile memory into the volatile memory(often organized in a hierarchy) for execution by the processors of theelectronic device.

A network device (ND) is an electronic device that communicativelyinterconnects other electronic devices on the network (e.g., othernetwork devices, end-user devices). Some network devices are “multipleservices network devices” that provide support for multiple networkingfunctions (e.g., routing, bridging, switching, Layer 2 aggregation,session border control, Quality of Service, and/or subscribermanagement), and/or provide support for multiple application services(e.g., data, voice, and video). Network devices or network elements caninclude APs and non-AP STAs in wireless communications systems such as aWLAN. STAs are devices connected to and communicating in a WLANincluding client or user devices that connect to the WLAN via APs. APsare network devices that may be specialized wireless access points thatcan communicate with other network devices in the WLAN via the wirelessmedium or via wired connections. A STA or AP may be referred to hereinas a WLAN device.

In a task group called Institute of Electrical and Electronics Engineers(IEEE) 802.11ax, High Efficiency WLAN (HEW) standardization is underdiscussion. The HEW aims at improving performance felt by usersdemanding high-capacity and high-rate services. The HEW may support ULMU (MU) simultaneous transmission, which includes UL MU Multiple-InputMultiple-Output (MU-MIMO) and UL Orthogonal Frequency Division MultipleAccess (OFDMA) transmissions.

Typically, an AP initiates a UL MU simultaneous transmission bytransmitting a trigger frame (sometimes referred to as a UL-Poll frame)to a set of STAs that are to participate in the UL MU simultaneoustransmission. The trigger frame may serve various purposes. One purposeof the trigger frame is to provide a reference to the STAs that are toparticipate in the UL MU simultaneous transmission in terms of time.Another purpose of the trigger frame is to provide informationpertaining to the UL MU simultaneous transmission such as a list of STAsthat are to participate in the UL MU simultaneous transmission, theassignment of transmission resources to STAs, and other physical layer(PHY) attributes and media access control (MAC) layer attributespertaining to the UL MU simultaneous transmission that the STAs that areto participate in the UL MU simultaneous transmission may need to knowto properly transmit their respective payloads to the AP during the ULMU simultaneous transmission. In response to receiving the triggerframe, the STAs that participate in the UL MU simultaneous transmissiontransmit their respective payloads simultaneously to the AP during theUL MU simultaneous transmission according to the information indicatedin the trigger frame (e.g., using an assigned transmission resource), inthe form of a UL MU PPDU.

The present disclosure defines various fields (and subfields thereof)that may be included in a trigger frame that initiates a UL MUsimultaneous transmission. An AP may set the values in these fields ofthe trigger frame to convey various attributes pertaining to the UL MUPPDU that is to be transmitted by the STAs that participate in the UL MUsimultaneous transmission. The AP may then transmit the trigger frame tothe STAs that are to participate in the UL MU simultaneous transmission.The STAs that receive the trigger frame may determine how to properlyform the UL MU PPDU based on the attributes pertaining to the UL MU PPDUindicated in the trigger frame.

As will be described in additional detail below, in one embodiment, atrigger frame that initiates a UL MU simultaneous transmission includesa UL MU PPDU attributes field. The UL MU PPDU attributes field (alsoreferred to herein as “common info field”) is used to indicateattributes pertaining to the UL MU PPDU that are common to all the STAsthat are scheduled to participate in the UL MU simultaneoustransmission. In one embodiment, the trigger frame also includes one ormore STA PSDU attributes fields. Each of the one or more STA PSDUattributes fields (also referred to herein as “per-user info field”) isused to indicate attributes pertaining to the UL MU PPDU that arespecific to a particular STA from the STAs that are scheduled toparticipate in the UL MU simultaneous transmission. In one embodiment, atrigger frame may include a single UL MU PPDU attributes field andmultiple STA PSDU attributes field (e.g., one STA PSDU attributes fieldfor each STA that is scheduled to participate in the UL MU simultaneoustransmission or a subset thereof).

FIG. 1 is a diagram illustrating operations of a UL MU simultaneoustransmission, according to some embodiments. For sake of clarity andease of understanding, the operations are described in the context of aWLAN that includes an AP and at least four STAs (e.g., STA1, STA2, STA3,and STA4). It should be understood, however, that the embodimentsdescribed herein are not limited to this context. In the diagram, thehorizontal dimension represents the time dimension (or number ofOrthogonal Frequency-Division Multiplexing (OFDM) symbols), while thevertical dimension represents the frequency dimension (or number oftones or number of subcarriers). The AP may initiate a UL MUsimultaneous transmission by transmitting a trigger frame in aunicast/multicast/broadcast manner such that all of the intendedparticipants of the UL MU simultaneous transmission can receive anddecode the trigger frame. In this example, the intended participants ofthe UL MU simultaneous transmission are STA1, STA2, STA3, and STA4.Although shown as a single trigger frame transmitted in a PPDU, in otherembodiments, the PPDU may include multiple trigger frames thatcollectively schedule the UL MU transmission. For the sake ofsimplicity, a PPDU carrying a single trigger frame will be describedhereinafter. After a predetermined time (e.g., Short Interframe Space(SIFS) time) from receiving the trigger frame (or the PPDU carrying thetrigger frame), the STAs that participate in the upcoming UL MUsimultaneous transmission simultaneously transmit a preamble followed bytheir respective payloads to the AP during the UL MU simultaneoustransmission, which forms a UL MU PPDU. The preamble may include symbolssuch as legacy short training field (L-STF), legacy long training field(L-LTF), legacy signal field (L-SIG), and High Efficiency signal field(HE SIG). Each STA transmits its payload during the UL MU simultaneoustransmission using a transmission resource (e.g., a transmissionresource unit) assigned to itself (e.g., the assignment of transmissionresources to STAs may be indicated in the trigger frame). The payload ofeach STA may be transmitted in a PSDU. In this example, STA1 transmitsits payload using a first transmission resource (or the transmissionresource identified within the first per-user info field), STA2transmits its payload using a second transmission resource, STA3transmits its payload using a third transmission resource, and STA4transmits its payload using a fourth transmission resource.

In one embodiment, a trigger frame that initiates a UL MU simultaneoustransmission includes a UL MU PPDU attributes field. The UL MU PPDUattributes field is used to indicate attributes pertaining to a UL MUPPDU that is to be transmitted to the AP during the UL MU simultaneoustransmission that are common to all the STAs that are scheduled toparticipate in the UL MU simultaneous transmission. These attributes maybe referred to herein as UL MU PPDU attributes. In one embodiment, thetrigger frame also includes one or more STA PSDU attributes fields. EachSTA PSDU attributes field is used to indicate attributes pertaining tothe UL MU PPDU that are specific to a particular STA that is scheduledto participate in the UL MU simultaneous transmission. These attributesmay be referred to herein as STA PSDU attributes. In one embodiment, atrigger frame may include a single UL MU PPDU attributes field andmultiple STA PSDU attributes field (e.g., one STA PSDU attributes fieldfor each STA that is scheduled to participate in the UL MU simultaneoustransmission or a subset thereof). In one embodiment, the UL MU PPDUattributes field and each of the STA PSDU attributes fields havevariable length, but there may be a fixed maximum length for each field.In one embodiment, one or more subfields of the UL MU PPDU attributesfield and/or a STA PSDU attributes field may not be present depending onthe value in one or more of the other subfields.

The UL MU PPDU attributes field may include one or more subfields suchas a persistent trigger subfield, a bandwidth subfield, a MU PPDU typesubfield, a guard interval subfield, a duration subfield, a groupidentifier subfield, an access category subfield, an access categoryrestriction subfield, a padding subfield, and a P matrix size subfield.An AP may set the values in these subfields to convey various attributespertaining to the UL MU PPDU that are common to all the STAs that arescheduled to participate in the UL MU simultaneous transmission. Thestructure and interpretation of these subfields are further describedherein below.

The persistent trigger subfield of the UL MU PPDU attributes field maybe used to indicate whether one or more of the attributes pertaining tothe UL MU PPDU is the same as indicated in a previously transmittedtrigger frame. In one embodiment, the length of the persistent triggersubfield is one bit, where a first state of the bit (e.g., “1” or TRUEvalue) indicates that the UL MU PPDU attributes are the same asindicated in the preceding trigger frame and a second state of the bit(e.g., “0” or FALSE value) indicates that the UL MU PPDU attributes arenot the same as indicated in the preceding trigger frame. In the casethat the bit is set to the first state (which indicates that the UL MUPPDU attributes are the same as indicated in the preceding triggerframe), some of the other subfields of the UL MU PPDU attributes fieldmay not be present in the UL MU PPDU attributes field. In the case thatthe bit is set to the second state (which indicates that the UL MU PPDUattributes are not the same as indicated in the preceding triggerframe), all of the subfields of the UL MU PPDU attributes field may bepresent in the UL MU PPDU attributes field. In one embodiment, thelength of the persistent trigger subfield is more than one bit. In thiscase, the value in the persistent trigger subfield serves as anidentifier that identifies a previously transmitted trigger frame. Inone embodiment, if the value in the persistent trigger subfield of atrigger frame is set to a value that has appeared in the persistenttrigger subfield of a previous trigger frame during the currenttransmission opportunity (TXOP), then this indicates that some or all ofthe UL MU PPDU attributes are the same as indicated in the previoustrigger frame. In this case, some of the subfields of the UL MU PPDUattributes field may not be present in the trigger frame. In oneembodiment, if the value in the persistent trigger subfield is set to avalue that has not appeared in the persistent trigger subfield of anyprevious trigger frame during the current TXOP, then this indicates thatthe UL MU PPDU attributes are not the same as indicated in any previoustrigger frame. In this case, all of the subfields of the UL MU PPDUattributes filed may be present in the trigger frame. As mentionedabove, in one embodiment, if the value in the persistent triggersubfield is set to the first state or is set to a value that hasappeared in the persistent trigger subfield of a previous trigger frameduring the current TXOP, then one or more of the subfields of the UL MUPPDU attributes field may not be present in the trigger frame. However,in some embodiments, some subfields of the UL MU PPDU attributes fieldthat happen to be located within the same byte-boundary as thepersistent trigger subfield may be present. For example, in oneembodiment, the bandwidth subfield and UL MU PPDU type subfield may bewithin the same byte-boundary as the persistent trigger subfield, andthus these subfields may appear in the UL MU PPDU attributes field evenwhen they are not needed. In one embodiment, the bandwidth subfield, ULMU PPDU type subfield, and duration subfield may be within the samebyte-boundary as the persistent trigger subfield, and thus thesesubfields may appear in the UL MU PPDU attributes field even when theyare not needed. In one embodiment, if the value in the persistenttrigger subfield is set to the first state (e.g., set to “1” or TRUEvalue) or is set to a value that has appeared in the persistent triggersubfield of a previous trigger frame during the current TXOP, then thisindicates that the STA PSDU attributes are the same as indicated in theimmediately preceding trigger frame or the indicated previous triggerframe. In this case, a STA PSDU attributes field may not be present inthe trigger frame.

The bandwidth subfield of the UL MU PPDU attributes field is used toindicate a bandwidth of the UL MU PPDU. For instance, this subfieldcould indicate that the upcoming UL MU PPDU is a 20 MHz, 40 MHz, 80 MHz,80+80 MHz, or 160 MHz PPDU.

The MU PPDU type subfield of the UL MU PPDU attributes field is used toindicate whether the UL MU PPDU is a UL MU MIMO PPDU.

The guard interval subfield of the UL MU PPDU attributes field is usedto indicate a guard interval (GI) or cyclic prefix (CP) that the STAsthat participate in the UL MU simultaneous transmission are to apply toone or more portions of the UL MU PPDU.

The duration subfield of the UL MU PPDU attributes field is used toindicate the length of the UL MU PPDU.

The group identifier subfield of the UL MU PPDU attributes field is usedto indicate a group identifier that associates a group of the STAs thatparticipate in the UL MU simultaneous transmission to form the UL MUPPDU.

The access category subfield of the UL MU PPDU attributes field is usedto indicate an allowed access category for data included in the UL MUPPDU, or the access category that the AP used the associated EnhancedDistributed Channel Access (EDCA) contention parameters to access themedium with. The allowed access category for data included in the UL MUPPDU is a category/type of data that is allowed to be transmitted in theUL MU PPDU. In one embodiment, the value in the access category subfieldindicates that the allowed access category is voice (VO), video (VI),background (BK), or best effort (BE).

The access category restriction subfield of the UL MU PPDU attributesfield is used to indicate whether all of the STAs that participate inthe UL MU simultaneous transmission to form the UL MU PPDU are to abideby the same access category setting indicated in the access categorysubfield. In one embodiment, the access category restriction subfield isused to indicate that the STAs are restricted to transmitting data inthe UL MU PPDU that belongs to the same access category as indicated inthe access category subfield or that belongs to an access category thathas a higher priority.

The padding subfield of the UL MU PPDU attributes field is used toindicate whether the STAs that participate in the UL MU simultaneoustransmission to form the UL MU PPDU are to apply padding to the UL MUPPDU. In one embodiment, if the value in the padding subfield is set toa first value (e.g., “1” or TRUE value), then this indicates that theSTAs that form the UL MU PPDU are to apply a padding procedure to padthe UL MU PPDU. However, if the value in the padding subfield is set toa second value (e.g., “0” or FALSE value), then this indicates that theSTAs that form the UL MU PPDU may or may not apply a padding procedureto pad the UL MU PPDU (i.e., padding may be optional). In oneembodiment, the value in the padding subfield indicates a paddingsetting for each sub-channel. For example, the value in the paddingsubfield may indicate a separate padding setting for each 20 MHzsub-channel. In one embodiment, if the value in the padding subfield fora particular sub-channel indicates that padding is to be applied forthat particular sub-channel, then this indicates that all of the STAsthat are assigned a transmission resource in that particular sub-channelare to apply a padding procedure to pad the UL MU PPDU. However, if thevalue in the padding subfield for a particular sub-channel indicatesthat padding is optional for that particular sub-channel, then thisindicates that all of the STAs that are assigned a transmission resourcein that particular sub-channel may or may not apply a padding procedureto pad the UL MU PPDU (i.e., padding may be optional).

The P matrix size subfield of the UL MU PPDU attributes field is used toindicate the size of a P matrix that the STAs that participate in the ULMU simultaneous transmission are to use to generate their respective setof HE LTF symbols in the UL MU PPDU. If the AP assigns a maximum of twospatial streams to one or more of the STAs that are identified in aTrigger frame, then the P matrix size is two and all the STAs identifiedin the Trigger frame use the square P matrix with size two to generatetwo LTF sequences for the UL MU PPDU. Therefore, identifying the Pmatrix size identifies the number of LTF sequences that all the STAs aregoing to generate and use in the UL MU PPDU. The UL MU PPDU attributesfield may also have a Type subfield, where the sender of the triggerframe requests the recipients thereof to send a response frame with thespecified type. In some embodiments, the Type subfield appears as thefirst subfield in the UL MU PPDU attributes field.

The STA PSDU attributes field for a particular STA may include one ormore subfields such as a STA identifier subfield, a new assignmentidentification subfield, an assignment subfield, a modulation codingscheme (MCS) subfield, a number of spatial streams subfield, a paddingsubfield, and a P matrix rows subfield. An AP may set the values inthese subfields to convey various attributes pertaining to the UL MUPPDU that are specific to the particular STA. The structure andinterpretation of these subfields are further described herein below.

The STA identifier subfield of the STA PSDU attributes field for aparticular STA is used to indicate an association identifier assigned tothe particular STA. In one embodiment, the value in the STA identifiersubfield is an association ID (AID), partial AID (PAID), or another formof AID/PAID.

The new assignment identification subfield of the STA PSDU attributesfield for a particular STA is used to indicate whether the transmissionresource assigned to the particular STA is the same as indicated in apreviously transmitted trigger frame. In one embodiment, if the value inthe new assignment identification subfield indicates that thetransmission resource assigned to the particular STA is the same asindicated in a previously transmitted trigger frame, then some of theother subfields (e.g., assignment subfield) of the STA PSDU attributesfield for the particular STA may not be present in the trigger frame. Inone embodiment, if the value in the new assignment identificationsubfield indicates that the transmission resource assigned to theparticular STA is not the same as indicated in a previously transmittedtrigger frame, then all of the subfields of the STA PSDU attributesfield for the particular STA may be present in the trigger frame.

The assignment subfield of the STA PSDU attributes field for aparticular STA is used to indicate a transmission resource that theparticular STA is to use to transmit a set of Media Access Control (MAC)Protocol Data Units (MPDUs) within the UL MU PPDU to the AP during theUL MU simultaneous transmission. In one embodiment, in the case that theUL MU PPDU is not a UL MU MIMO PPDU, the value in the assignmentsubfield indicates the sub-band index or set of indices that theparticular STA is to use to transmit a set of MPDUs within the UL MUPPDU to the AP during the UL MU simultaneous transmission. In oneembodiment, the value in the assignment subfield is a reserved value ormay not be present if the UL MU PPDU is a UL MU MIMO PPDU.

The MCS subfield of the STA PSDU attributes field for a particular STAis used to indicate an MCS level that the particular STA is to use forone or more portions of the UL MU PPDU that is to be transmitted to theAP during the UL MU simultaneous transmission.

The number of spatial streams subfield of the STA PSDU attributes fieldfor a particular STA is used to indicate the number of spatial streamsthat the particular STA is to use to transmit the UL MU PPDU to the APduring the UL MU simultaneous transmission. In an embodiment, the valuein the number of spatial streams subfield along with the value in the Pmatrix rows subfield define the set of spatial streams assigned to aSTA, where the value in the P matrix rows subfield identifies thestarting spatial reuse index.

The padding subfield of the STA PSDU attributes field for a particularSTA is used to indicate whether the particular STA is to apply paddingto the UL MU PPDU. In one embodiment, if the value in the paddingsubfield is set to a first value (e.g., “1” or TRUE value), then thisindicates that the particular STA is to apply a padding procedure to padthe UL MU PPDU. However, if the value in the padding attribute is set toa second value (e.g., “0” or FALSE value), then this indicates that theparticular STA may or may not apply a padding procedure to pad the UL MUPPDU (padding is optional).

The P matrix rows subfield of the STA PSDU attributes field for aparticular STA is used to indicate a set of rows of a P matrix that theparticular STA is to use to generate a set of HE LTF symbols in the ULMU PPDU, as well as the set of spatial streams that the STA is to use.In one embodiment, the value in the P matrix rows subfield may indicatea single row of the P matrix that is assigned to the particular STA orindicate a set of rows of the P matrix (the size of which may beindicated in the P matrix size subfield of the UL MU PPDU attributesfield) that the particular STA is to use to generate its set of HE LTFsymbols. In one embodiment, the “P matrix rows” subfield and the “numberof spatial streams” subfield collectively identify the spatial streams(SS) allocation that the AP assigns to a STA.

In one embodiment, the group identifier subfield and the persistenttrigger subfield of a UL MU PPDU attributes field can share the samesubfield (e.g., the subfield can serve as either a group identifiersubfield or a persistent trigger subfield), where the value in the MUPPDU type subfield indicates the role of the subfield. For example, whenthe value in the MU PPDU type subfield indicates that the UL MU PPDU isa UL MU MIMO PPDU, then the shared subfield is interpreted as a groupidentifier subfield. When the value in the MU PPDU type subfieldindicates that the UL MU PPDU is a UL MU OFDMA PPDU, then the sharedsubfield is interpreted as a persistent trigger subfield.

In one embodiment, the UL MU PPDU attributes field may include a mapsubfield. The length of the map subfield could be any number of bytes,depending on the number of STAs that are indicated in the trigger frame.In one embodiment, the value in the map subfield is a reserved value (orthe map subfield is not included) in a trigger frame where the value inthe persistent trigger subfield is a value that appears for the firsttime in a TXOP. In one embodiment, when the value in the persistenttrigger subfield of a trigger frame is a value that appears for thesecond or more time in a TXOP, each bit in the map subfield indicateswhether the STA whose STA PSDU attributes field appeared with the sameorder value as the bit order of that bit in the first trigger frame(where the value in the persistent trigger subfield was set to the samevalue as the value in the persistent trigger subfield of the currenttrigger frame) is assigned a transmission resource in the currenttrigger frame or not. If the bit is set to a first state (e.g., “0” orFALSE value), then this indicates that there is no STA PSDU attributesfield for the STA represented by that bit in the current trigger frame.However, if the bit is set to a second state (e.g., “1” or TRUE value),then this indicates that there is a STA PSDU attributes field for theSTA represented by that bit in the current trigger frame. For example,if a trigger frame includes an indication that eight STAs are toparticipate in the UL MU simultaneous transmission and the trigger frameincludes a persistent trigger subfield with a value that has appearedfor the first time in a TXOP, then the value in all bits in the mapsubfield (which has a length of 1 byte (or eight bits)) may have areserved value. In a subsequent trigger frame, where the value in thepersistent trigger subfield has the same value as the value in thepersistent trigger subfield of the first trigger frame, the first bit ofthe map subfield indicates whether a STA PSDU attributes field for theSTA whose STA PSDU attributes field appeared first in the first triggerframe is included in the subsequent trigger frame. Other bits of the mapsubfield can be interpreted in a similar fashion.

In one embodiment, the STA identifier subfield and the new assignmentidentification subfield of a STA PSDU attributes field have a totalcombined length of two bytes. In one embodiment, these two subfields arealways present in a STA PSDU attributes field, but depending on thevalue in the new assignment identification subfield, other subfields ofthat STA PSDU attributes field may or may not present in that STA PSDUattributes field (e.g., according to the rules described above withreference to the new assignment identification subfield).

In one embodiment, the persistent trigger subfield of the UL MU PPDUattributes field has a length ranging between one to two bytes. In oneembodiment, depending on the value in the persistent trigger subfield,other subfields of the UL MU PPDU attributes field may or may not bepresent in the UL MU PPDU attributes field (e.g., according to the rulesdescribed above with reference to the persistent trigger subfield).

In one embodiment, a trigger frame includes a single UL MU PPDUattributes field and two or more STA PSDU attributes fields, where theUL MU PPDU attributes field and the two or more STA PSDU attributesfields each include all of the subfields for that field. In oneembodiment, a trigger frame includes a UL MU PPDU attributes field,where the UL MU PPDU attributes field only includes a subset of thesubfields for a UL MU PPDU attributes field (e.g., persistent triggersubfield and one or more other subfields). In one embodiment, a triggerframe includes two or more STA PSDU attributes fields, where one of theSTA PSDU attributes fields includes all of the subfields for a STA PSDUattributes field, and where another one of the STA PSDU attributesfields only includes a STA identifier subfield and a new assignmentidentification subfield. In one embodiment, a trigger frame includes aUL MU PPDU attributes field, where the UL MU PPDU attributes fieldincludes all or a subset of the subfields for a UL MU PPDU attributesfield, and where the value in the persistent trigger subfield of the ULMU PPDU attributes field indicates that the STA PSDU attributes are thesame as indicated in the preceding trigger frame or previous triggerframe. In this case, the trigger frame may not include a STA PSDUattributes field.

In an embodiment where the length of the persistent trigger subfield isone bit, the following rules may apply. When an AP sets the value in thepersistent trigger subfield of a UL MU PPDU attributes field to indicatethat the UL MU PPDU attributes are not the same as indicated in thepreceding trigger frame, then the AP should include all of the subfieldsfor a UL MU PPDU attributes field in the UL MU PPDU attributes field andalso include two or more STA PSDU attributes fields in the triggerframe, each including all of the subfields for a STA PSDU attributesfield. An AP should not transmit a trigger frame with the value in thepersistent trigger subfield of the UL MU PPDU attributes field set toindicate that the UL MU PPDU attributes are the same as indicated in thepreceding trigger frame to a STA that does not have UL MU persistentcapability (e.g., the capability to remember the UL MU PPDU attributesand STA PSDU attributes indicated in a previous trigger frame). An APshould not transmit a trigger frame with the value in the persistenttrigger subfield of the UL MU PPDU attributes field set to indicate thatthe UL MU PPDU attributes are the same as indicated in the precedingtrigger frame in the first trigger frame transmitted in a TXOP. A STAthat has UL MU persistent capability that receives a first trigger framewith the value in the persistent trigger subfield of the UL MU PPDUattributes field set to indicate that the UL MU PPDU attributes are notthe same as indicated in the preceding trigger frame and that includes aSTA PSDU attributes field for the STA (e.g., the value in the STAidentifier subfield of the STA PSDU attributes field identifies the STA)should store the UL MU PPDU attributes indicated in the UL MU PPDUattributes field and the STA PSDU attributes indicated in the STA PSDUattributes field for at least the remainder of the TXOP duration. If theSTA subsequently receives a second trigger frame with the value in thepersistent trigger subfield of the UL MU PPDU attributes field set toindicate that the UL MU PPDU attributes are the same as indicated in thepreceding trigger frame, the STA should use the stored attributes todetermine how to transmit the UL MU PPDU that follows the second triggerframe.

In an embodiment where the length of the persistent trigger subfield ismore than one bit, the following rules may apply. When an AP sets thevalue in the persistent trigger subfield of a UL MU PPDU attributesfield to a value that appears for the first time in a TXOP, then the APshould include all of the subfields for a UL MU PPDU attributes field inthe UL MU PPDU attributes field and also include two or more STA PSDUattributes fields in the trigger frame, each including all of thesubfields for a STA PSDU attributes field. When an AP transmits atrigger frame to a STA that does not have UL MU persistent capability,the AP should transmit the trigger frame with the value in thepersistent trigger subfield set to a value different than the value inthe persistent trigger subfield of any of the previous trigger framestransmitted in the TXOP. A STA that has UL MU persistent capability thatreceives a first trigger frame, where the value in the persistenttrigger subfield of the UL MU PPDU attributes field is set to a valuethat appears for the first time in the TXOP and that includes a STA PSDUattributes field for the STA (e.g., the value in the STA identifiersubfield of the STA PSDU attributes field identifies the STA), shouldstore the UL MU PPDU attributes indicated in the UL MU PPDU attributesfield and the STA PSDU attributes indicated in the STA PSDU attributesfield for at least the remainder of the TXOP duration. If the STAsubsequently receives a second trigger frame, where the value in thepersistent trigger subfield of the UL MU PPDU attributes field is set tothe same value as in the persistent trigger subfield of the firsttrigger frame, the STA should use the stored attributes to determine howto transmit the UL MU PPDU that follows the second trigger frame.

In one embodiment, the attributes (e.g., UL MU PPDU attributes and STAPSDU attributes) indicated in a trigger frame are valid during a givenTXOP duration (and a STA stores the attributes at least for the durationof the TXOP, as described above). In other embodiments, the attributesindicated in a trigger frame are valid during a beacon interval in whichthe trigger frame was transmitted (and a STA stores the attributes atleast for the duration of the beacon interval).

In one embodiment, an AP may obtain a TXOP before transmitting a triggerframe. During the TXOP, the AP may transmit the trigger frame to a groupof STAs, and the AP may expect to receive a UL MU PPDU from the group ofSTAs.

In one embodiment, a STA transmits a frame (e.g., data frame, managementframe, or control frame) to an AP that the STA is associated with, wherethe frame indicates the queue size at the STA (e.g., either for the sameaccess category as the data in the data frame or for all accesscategories). After receiving the frame from the STA, the AP may transmita trigger frame and initiate a TXOP. In this embodiment, beforetransmitting a data frame to the AP, the STA may perform a backoffprocedure according to the rules for the access category to which thedata in the data frame belongs (e.g., the STA performs backoff with avalue of AIFS[AC]+backoff_value, where backoff_value is a randomlychosen according to contention rules). In one embodiment, the data frameincludes an indication of a queue size at the STA for the same accesscategory as the data in the data frame or for all access categories.After the AP receives the data frame from the STA, it transmits anyrelevant ACK frames or Block ACK frames that is required by the dataframe. Then, depending on the queue size indicated in the data framereceived from the STA, the AP may decide to transmit a trigger frame toinitiate a UL MU simultaneous transmission (e.g., either UL MU OFDMAtransmission or UL MU MIMO transmission) in which the STA is assigned atransmission resource. In such a case, the AP may not need to performany back-off before transmitting the trigger frame, but may transmit thetrigger frame after SIFS or Point Coordination Function (PCF) IFS (PIFS)time with appropriate values to initiate a TXOP. The reason that the APmay refrain from performing back-off and start the TXOP after an IFStime after receiving the frame from the STA is because the STA hasalready performed the necessary backoff and since the AP is going totransmit a trigger frame that initiates a UL MU simultaneoustransmission in which the STA is assigned a transmission resource, thereis no loss of fairness. This is similar to the situation in which a STAand an AP have jointly performed a full back-off according to thecontention rules. This concept is referred to as joint back-off andrefers to the concept where as long as a STA has performed back-offaccording to the contention rule, the responding STA (which in this caseis the AP that is going to transmit a trigger frame to initiate a UL MUsimultaneous transmission) need not perform back-off again, as long asthe trigger frame initiates a UL MU simultaneous transmission in whichthe STA is assigned a transmission resource and as long as databelonging to an access category that is lower priority than the accesscategory of the data in the initial frame received from the STA is notallowed to be transmitted during the UL MU simultaneous transmission. Inone embodiment, the access category constraint might be further limitedso that the responding STA (e.g., the AP) is to only transmit a triggerframe that initiates a UL MU simultaneous transmission in which databelonging to an access category that is the same as the access categoryof the data in the initial frame received from the STA is allowed. Inanother embodiment, the access category constraint might be lifted sothat the responding STA (e.g., the AP) may transmit a trigger frame thatinitiates a UL MU simultaneous transmission in which data belonging toall access categories is allowed. In one embodiment, a STA firsttransmits a data or management frame to the AP that includes anindication of a queue size at the STA and the AP transmits a triggerframe that includes an indication that all of the STAs that participatein a UL MU simultaneous transmission (including the STA that transmittedthe data or management frame to the AP) are to first respond with aclear-to-send (CTS) frame and then after a SIFS time transmit a UL MUPPDU to the AP as part of the UL MU simultaneous transmission. In thiscase, the duration field of the MAC header of the CTS frame may be setto the same value as indicated in the duration subfield of the triggerframe that initiated the UL MU simultaneous transmission minus theduration of the CTS frame and minus two SIFS time. In one embodiment,the duration of the CTS frame is calculated based on a robust MCS levelthat is known to the AP and STAs beforehand and all of the STAs use theknown MCS level to encode their CTS frame. In one embodiment, the framethat the STA first transmits to the AP could be a data frame that allowsdata belonging to any access category that the STA decides. In oneembodiment, the frame that the STA first transmits to the AP is aPS-Poll frame, a QoS Null data frame that allows data belonging to anyaccess category that the STA decides, or a UL Request frame. In oneembodiment, in the case that the STA transmits a PS-Poll frame to theAP, the AP may transmit a trigger frame after SIFS or PIFS time thatinitiates a UL MU simultaneous transmission in which only data belongingto the lowest priority access category is allowed, otherwise the AP isto perform relevant backoff for the desired access category (e.g., theAP is to perform backoff with value AIFS[AC]+backoff_value beforetransmitting the trigger frame).

In the process of forming a UL MU PPDU, a new TXVECTOR parameter may beused, which is denoted by Power_Boost. The Power_Boost parameter is ascalar value which is used in HE OFDMA PPDU. The Power_Boost parameterin TXVECOTR is used by the MAC layer to tell the PHY layer how muchincreased transmission power, with respect to the power transmissionover a 20 MHz sub-band such transmission of legacy frame over theprimary 20 MHz channel, is allowed for the UL MU PPDU (e.g., UL MU OFDMAPPDU or UL MU MIMO PPDU). In one embodiment, the Power_Boost parameterin TXVECOTR is mandatory for UL OFDMA PPDUs.

When an AP transmits a trigger frame that initiates a UL MU simultaneoustransmission, the UL MU PPDU attributes field of the trigger frame mayinclude a duration subfield. Each STA that participates in the UL MUsimultaneous transmission may perform a padding procedure based on thebandwidth of a transmission resource assigned to itself. In a paddingprocedure, a STA pads its payload (either in MAC layer or PHY layer, orboth) so that the length of its UL MU PPDU is the same as the lengthindicated in the duration subfield of the UL MU PPDU attributes field ofthe trigger frame that initiated the UL MU simultaneous transmission.For example, if the bandwidth of the transmission resource assigned to aSTA is 2 MHz, then the STA may pad its payload accordingly. If thebandwidth of the transmission resource assigned to a STA is 4 MHz, thenthe STA may pad its payload accordingly. If the bandwidth of thetransmission resource assigned to a STA is equal to or larger than 10MHz, then the STA may pad its payload accordingly. If the bandwidth ofthe transmission resource assigned to a STA is equal to or larger than20 MHz, then the STA may pad its payload accordingly.

In one embodiment, if the bandwidth of a transmission resource assignedto a STA is 2 MHz and the Power_Boost parameter of the TXVECTOR of theUL OFDMA PPDU that the STA is about to transmit in response to a triggerframe is larger than a threshold value, then the STA may pad its payloadaccordingly. In one embodiment, if the bandwidth of a transmissionresource assigned to a STA is 4 MHz and the Power_Boost parameter of theTXVECTOR of the UL MU OFDMA PPDU that the STA is about to transmit inresponse to a trigger frame is larger than a threshold value, then theSTA may pad its payload accordingly. In one embodiment, if the value inthe relevant padding subfield (depending on embodiments, the paddingsubfield might apply to all of the STAs that are indicated in thetrigger frame or might apply to all of the STAs that are indicated inthe trigger frame for a given 20 MHz sub-band, or might apply to aspecific STA) indicates that a STA is to apply padding, then the STApads its payload accordingly. Otherwise if the value in the paddingsubfield indicates that padding is optional for the STA, then the STAmay or may not pad its payload.

When an AP transmits a trigger frame that initiates a UL MU simultaneoustransmission, where the trigger frame includes an indication of the setof STAs that are to participate in the UL MU simultaneous transmission,it is not guaranteed that all of the STAs in the set of STAssuccessfully receive the trigger frame correctly. As such, some of theSTAs might participate in the UL MU simultaneous transmission and someof the STAs might not. Thus, it is possible that the AP may successfullyreceive a UL payload, an MPDU, or an A-MPDU from some of the STAs butnot from all of the STAs during the UL MU simultaneous transmission.

In one embodiment, the exchange of trigger frame and subsequent UL MUPPDU is considered successful if at least one STA that is assigned atransmission resource in the primary 20 MHz channel responds to thetrigger frame. In other words, the exchange of trigger frame andsubsequent UL MU PPDU is considered successful if the AP successfullyreceives a UL MPDU/A-MPDU (e.g., aggregated MPDU) from at least one STAindicated in the trigger frame that is assigned a transmission resourcewithin the primary 20 MHz channel. In one embodiment, the exchange oftrigger frame and subsequent UL MU PPDU is considered successful if theAP successfully receives a UL MPDU/A-MPDU from all of the STAs indicatedin the trigger frame that are assigned a transmission resource withinthe primary 20 MHz channel.

In one embodiment, the STAs that did not respond to a first triggerframe should not be indicated in a subsequent trigger frame that istransmitted within the same TXOP as the first trigger frame. In oneembodiment, the STAs that did not respond to a first trigger frame andwere assigned to a transmission resource in the primary channel of theBSS should not be indicated as being assigned to a transmission resourcein the primary channel of the BSS in a subsequent trigger frame. In oneembodiment, the STAs that did not respond to a first trigger frameshould not be indicated in a subsequent trigger frame if the subsequenttrigger frame is transmitted within the same TXOP as the first triggerframe and if the same or lower MCS level as in the first trigger frameis used. In one embodiment, if an AP transmits a first trigger frame andsome of the STAs indicated in the first trigger frame do not respond, anAP may transmit a subsequent trigger frame to the same set of STAs asindicated in the first trigger frame or to a set of STAs that includepart or all of the STAs that did not respond to the first trigger frameonly if the AP includes an indication in the subsequent trigger framethat the STAs are to first respond with a CTS frame and then wait IFStime before transmitting a UL MU PPDU to the AP during the UL MUsimultaneous transmission.

In one embodiment, the UL MU PPDU attributes field of a trigger framemay include a cascade indication subfield. The cascade indicationsubfield is used to indicate whether a subsequent trigger frame isscheduled to be transmitted following the current trigger frame. Forexample, if the value in the cascade indication subfield is set to “1”or a TRUE value, then this indicates that a subsequent trigger framefollows the current trigger frame. Otherwise, the value in the cascadeindication subfield is set to “0” or FALSE value. A STA that receives atrigger frame may determine whether it should transition to a sleep ordoze state (e.g., power saving mode) based on the value in the cascadeindication subfield. However, the value in the cascade indicationsubfield does not help the STA determine the approximate time at whichthe next trigger frame will be transmitted. As such, the STA does notknow when it should transition to an awake state in order to receive thenext trigger frame.

In one embodiment, an AP (e.g., HE AP) may indicate, in a beacon frame,the start times of one or more trigger frames that the AP is scheduledto transmit in the future. For example, in one embodiment, the beaconframe may include target wake time (TWT) information that indicates thetime at which one or more trigger frames will be transmitted within aservice period (SP) or a beacon interval (BI), where the one or moretrigger frames may initiate a UL MU simultaneous transmission thatallows random access. However, it is not unusual for a STA to miss oneor more beacon frames due to the STA being in a sleep or doze state(e.g., to save power) or due to collisions. If a STA misses a beaconframe, the STA will miss all the TWT information included in that beaconframe, and unless it stays in an awake state for a long period of time,it will miss any future trigger frames.

FIG. 2 is a diagram illustrating operations in a WLAN where a STA missesa beacon frame transmitted by an AP and thus is unaware of the starttime of trigger frame transmissions, according to some embodiments. Asshown in the diagram, an AP transmits a beacon frame that includesinformation regarding the start times of scheduled trigger frametransmissions. For example, the beacon frame may include informationregarding the start times of trigger frames Trigger 1, Trigger 2, andTrigger 3. In this example, STA1 misses the beacon frame due to acollision or due to being in a sleep state (e.g., doze state). As such,STA1 is unaware of the start times of trigger frames Trigger 1, Trigger2, and Trigger 3.

Embodiments described herein alleviate this problem by includinginformation regarding a future trigger frame (e.g., including the starttime of the future trigger frame) in a trigger frame. This way, even ifa STA misses the beacon frame, it can still become aware of the starttime of future trigger frames. For this purposes, the UL MU PPDUattributes field of a trigger frame may include a cascade trigger infosubfield (sometimes referred to as a next trigger info subfield), wherethe cascade trigger info subfield is used to indicate informationregarding a future trigger frame that is scheduled to be transmitted byAP. For example, if the value in the cascade indication subfield of atrigger frame indicates that a subsequent trigger frame is scheduled tobe transmitted, then the trigger frame also includes the cascade triggerinfo subfield, which includes information regarding the subsequenttrigger frame. In one embodiment, the information regarding thesubsequent trigger frame includes information regarding the time atwhich the subsequent trigger frame is scheduled to be transmitted (thestart time of the subsequent trigger frame). This may be indicated as arelative time reference to the beginning or end of the current triggerframe (or a relative time reference to the end of the UL MU PPDU thatfollows the trigger frame) in units of any time unit (TU).

FIG. 3 is a diagram illustrating operations in a WLAN where even thougha STA misses a beacon frame transmitted by an AP, the STA becomes awareof the start time of trigger frame transmissions based on informationincluded in a trigger frame, according to some embodiments. As shown inthe diagram, an AP transmits a beacon frame that includes informationregarding the start times of scheduled trigger frame transmissions. Forexample, the beacon frame may include information regarding the starttimes of trigger frames Trigger 1, Trigger 2, and Trigger 3. In thisexample, STA1 misses the beacon frame due to a collision or due to beingin a sleep state (e.g., doze state). Subsequently, the AP transmits atrigger frame Trigger 1, where this trigger frame includes informationregarding the start time of trigger frame Trigger 2 (represented as Δ2).When STA1 receives trigger frame Trigger 1, it can determine the time atwhich the AP will transmit trigger frame Trigger 2 based on Δ2. Triggerframe Trigger 2 may also include information regarding the start time oftrigger frame Trigger 3 (represented as Δ3). When STA1 receives triggerframe Trigger 2, it can determine the time at which the AP will transmittrigger frame Trigger 3 based on Δ3.

In one embodiment, the value in the cascade trigger info subfield is setto a reserved value (e.g., all-zero or all-one value) to indicate thatthere is no subsequent trigger frame scheduled to be transmitted in thecurrent beacon interval or SP. In one embodiment, the value in thecascade trigger info subfield is set to another reserved value toindicate that there is a subsequent trigger frame scheduled to betransmitted in the current beacon interval or SP, but that the starttime of the subsequent trigger frame is not available or not determinedby the AP. Different embodiments may utilize different TU to indicatethe timing information regarding a trigger frame. In one embodiment, TUis a fraction of target beacon transmission time (TBTT), such as onehundredth of a TBTT. In one embodiment, TU is a time value such as 10microseconds or 100 microseconds. In one embodiment, the value in thecascade trigger info subfield indicates timing information for asubsequent trigger frame that is scheduled to be transmitted in thecurrent beacon interval or the next beacon interval. In one embodiment,the value in the cascade trigger info subfield indicates whether atrigger frame is scheduled to be transmitted in the next beacon interval(where it is assumed that the trigger frame appears with a given timereference to a beacon frame). In one embodiment, a trigger frameincludes multiple cascade trigger info subfields, where the value in thefirst cascade trigger info subfield indicates timing informationregarding a first trigger frame that is scheduled to be transmitted andwhere the value in the second cascade trigger info subfield indicatestiming information regarding a second trigger frame that is scheduled tobe transmitted, and so on. In such embodiments, the total number ofcascade trigger info subfields may be known to all of the associatedSTAs, or another field or subfield within the trigger frame may indicatethe total number of cascade trigger info subfields.

In one embodiment, a cascade trigger info subfield is included in atrigger frame that initiates a UL MU simultaneous transmission thatallows random access (e.g., where the trigger frame does notspecifically indicate the group of STAs that are to participate in theUL MU simultaneous transmission, but instead a group of STAs areeligible to choose a transmission resource from the transmissionresources indicated in the trigger frame that allow random access). Atrigger frame that initiates a UL MU simultaneous transmission thatallows random access is sometimes referred to herein as a random accesstrigger frame (RA_TR frame). In one embodiment, when a RA_TR frameincludes a cascade trigger info subfield, the value in the cascadetrigger info subfield indicates timing information regarding a nextRA_TR frame that is scheduled to be transmitted (e.g., in the currentbeacon interval). In one embodiment, when a RA-TR frame includes acascade trigger info subfield, a STA that receives such RA-TR frame anddesires to transmit a payload in response to the RA-TR frame may attemptto do so based on the random access rules. It should be noted however,that executing the random access rules may result in the STA not beingable to transmit its payload in response to the RA-TR frame (e.g., dueto the instantaneous outcome of the execution of the random accessback-off rules). In such a case, the STA may determine the time at whicha subsequent RA-TR frame will be transmitted based on the value in thecascade trigger info subfield of the current trigger frame and then planto transmit its payload in response to the subsequent RA-TR frame. Inone embodiment, the STA may transition to a sleep or doze state untilthe time at which the subsequent RA-TR frame is expected to betransmitted and wake up around that time to receive the subsequent RA-TRframe. The STA may then execute the random access rules again to findout whether it is eligible to transmit its payload in response to thesubsequent RA-TR frame. In one embodiment, a STA might have had thechance to transmit its payload in response to a first RA-TR frame, butmay have not received an acknowledgement frame from the AP in responseto the frame that the STA transmitted during the random access phase.The reason for this may be that the AP did not successfully receive theframe transmitted by the STA or because there was a collision. In thecase that the STA does not receive an acknowledgement frame from the AP,the STA may determine the time at which a subsequent RA-TR frame will betransmitted based on the value in the cascade trigger info subfield ofthe current trigger frame and then plan to transmit its payload again inresponse to the subsequent RA-TR frame. In one embodiment, the STA maytransition to a sleep or doze state until the time at which thesubsequent RA-TR frame is expected to be transmitted and wake up aroundthat time to receive the subsequent RA-TR frame. The STA may thenexecute the random access rules to find out whether it is eligible totransmit its payload in response to the subsequent RA-TR frame. In oneembodiment, if a RA-TR frame includes multiple cascade trigger infosubfields (each representing a trigger frame that initiates a UL MUsimultaneous transmission that allows random access), a STA might chooseto participate in one or more of the upcoming random accessopportunities. If the STA decides to skip the first random accessopportunity and instead participate in the second random accessopportunity, then the STA may transition to a sleep or doze state for aduration that is determined based on the values in the first cascadetrigger info subfield and/or the second cascade trigger info subfield(e.g., the sum of the durations indicated in the first cascade triggerinfo subfield and the second cascade trigger info subfield).

In one embodiment, the value in the cascade trigger info subfield mayrepresent a timer, a time reference, or counter to the next triggerframe. For example the value in the cascade trigger info subfield mayrepresent a timer with a predetermined time unit that indicates thetiming of the next trigger frame (for a specific type of triggerframe—e.g., RA-TR frame). In one embodiment, the value in the cascadetrigger info subfield may indicate additional information such as thetrigger type and/or TWT Flow Identifier. In one embodiment, when thevalue in the cascade indication subfield is set to “1” or TRUE value(which indicates that a subsequent trigger frame is scheduled to betransmitted), the cascade trigger info subfield includes some of the TWTparameters such as Flow Identifier field value, or a full TWT elementIE. The TWT Flow Identifier field may be present in TWT Informationfield and it is a 3-bit subfield that identifies the specificinformation for this TWT request uniquely from other requests madebetween the same TWT requesting STA and TWT responding STA pair.

An AP may indicate the start times of one or more trigger frames thatinitiate a UL MU simultaneous transmission that allows random access ina beacon frame. A STA that receives such a beacon frame may transitionto a sleep or doze state until the time at which the AP is expected totransmit a trigger frame, as indicated in the beacon frame. In oneembodiment, if a sequence of trigger frames all initiate a UL MUsimultaneous transmission that allows random access, then all of thetrigger frames in this sequence should have its cascade indicationsubfield set to a value of 1, except for the last trigger frame in thesequence, which should have its cascade indication subfield set to avalue of “0” or FALSE value. In one embodiment, if a sequence of triggerframes all initiate a UL MU simultaneous transmission that allows randomaccess, then all but the last trigger frame in this sequence should haveits cascade indication subfield set to a value of “1” or TRUE value andshould include a cascade trigger info subfield that is set with a valuethat indicates timing information regarding a future trigger frametransmission. In one embodiment, the last trigger frame in this sequenceshould have its cascade indication subfield set to a value of “0” orFALSE value. In one embodiment, the last trigger frame in the sequencehas its cascade indication subfield set to a value of “1” or TRUE valueif there is another trigger frame that is scheduled to be transmitted inthe next beacon interval or the next SP. In this case, the value in thecascade trigger info subfield indicates timing information regarding afuture transmission of one or more trigger frames. In this case, thetrigger frame may also include an indication of whether the futuretrigger frame transmission will occur in the current beacon interval orSP or the next beacon interval or SP.

A STA may determine whether it should transition to a sleep or dozestate based on the value in the cascade indication subfield and/or thevalue in the cascade trigger info subfield of a trigger frame. If theOFDMA back-off (OBO) counter decrements to a non-zero value with therandom access procedure in a trigger frame, where the value in itscascade indication subfield set to “1” or TRUE value, it may transitionto a sleep or doze state immediately, and may use the value in thecascade trigger info subfield to determine when the next trigger frameis scheduled to be transmitted. The STA may then transition to an awakestate shortly before the next trigger frame is scheduled to betransmitted to receive the next trigger frame. If the OBO counterdecrements to a non-zero value with the random access procedure in atrigger frame, where the value in the cascade indication subfield set to“0” or FALSE value, it may remain in an awake state to receive the nexttrigger frame.

A STA that transmits a frame carrying a TWT element to a STA may set thevalue of the trigger subfield of the Request Type field of a TWT elementto 1, indicating a trigger-based TWT where the STA would have the chanceto transmit its UL data, without contending the medium, in one or moreUL MU PPDUs. Otherwise, the STA shall set the value of the triggersubfield to 0. In a TWT response, a trigger field set to 1 indicates atrigger enabled TWT. The TWT responding STA of a trigger-enabled TWTagreement should schedule for transmission of a trigger frame to the TWTrequesting STA, within each TWT SP for that TWT agreement. The TWTresponding STA that intends to transmit additional trigger frames duringa trigger-enabled TWT SP should set the value of the cascade indicationsubfield of the trigger frame to 1 to indicate that it will transmitanother trigger frame within the same TWT SP, and should include acascade trigger info subfield that includes a timer/counter to the oneor more upcoming trigger frames and possibly with an indication of thetrigger type, TWT Flow indicator (or other TWT parameters) of the one ormore upcoming trigger frames. Otherwise, the value of the cascadeindication subfield is set to 0.

The embodiments described herein are also applicable to trigger-enabledTWT service period (SP). In a trigger-enabled TWT SP, a TWT schedulingSTA (e.g., an AP) schedules a TWT SP that includes one or more triggerframes (where random access is allowed) and in response to the triggerframes within the SP one or more of the TWT scheduled STAs access thetrigger frames to transmit their payloads (e.g., to transmit a PS-Pollframe, QoS Null frames, data frames, etc.). In such cases, the TWTscheduling STA sets the trigger subfield in the Request Type field of aTWT element to “1” or TRUE value. The TWT scheduling STA that intends totransmit additional trigger frames during a Trigger-enabled TWT SPshould set the cascade indication subfield of the trigger frame to avalue of 1 to indicate that it will transmit another trigger framewithin the same TWT SP, and should include additional information in thecascade trigger info subfield such as a timer/counter to the one or moreof the upcoming trigger frames and possibly with trigger type indicationor Flow indication (or other TWT parameters) of the one or more of theupcoming trigger frames. Otherwise, it shall set the value of thecascade indication subfield to 0.

The embodiments described herein are also applicable to the cases wherea TWT scheduling STA (e.g., an AP) schedules multiple trigger-enabledTWT SPs within one beacon interval, where each trigger-enabled TWT SPincludes one or more trigger frames (which possibly includes at leastone transmission resource that allows random access), where one or moreTWT scheduled STAs access the one or more trigger frames within the oneor more of the trigger-enabled TWT SPs to transmit their payloads (e.g.,either PS-Poll frame, QoS Null frames, data frames, etc.). In such acase, the TWT scheduling STA indicates the beginning of an upcomingtrigger-enabled TWT SP (or the first trigger frame within an upcomingtrigger-enabled TWT SP) in the last trigger frame of the previoustrigger-enabled TWT SP. This may be indicated by setting the value ofthe cascade indication subfield to “1” or TRUE value and setting thevalue of the cascade trigger info to a value that indicates atimer/counter to the (one or more of the) upcoming trigger frames (andpossibly with trigger type indication, Flow indicator, or other TWTparameters) and possibly with another indicator that indicates that thenext trigger frame is in an upcoming trigger-enabled TWT SP. In onembodiment, the cascade trigger info subfield refers to the beginning ofthe upcoming trigger-enabled TWT SPs (and possibly with an indicationthat the cascade trigger info subfield refers to an upcomingtrigger-enabled TWT SPs.

In one embodiment, when a trigger frame is transmitted in SU manner(e.g., in a SU PPDU) and the value in the cascade indication subfield ofthe trigger frame is set to “1” or TRUE value, the value in the cascadetrigger info subfield of the trigger frame indicates informationregarding a trigger frame of the same type or the same Flow Indicator.

In one embodiment, when a trigger frame is transmitted in MU manner(e.g., in an MU PPDU) and the value in the cascade indication subfieldin the trigger frame is set to a “1” or TRUE value, the value in thecascade trigger info subfield in the trigger frame indicates informationregarding a trigger frame of the same type or the same Flow Indicator.

In one embodiment, all trigger frames transmitted in MU manner (e.g., inan MU PPDU) include information that points to the same type of triggerframe or the same Flow Indicator. In such case, the value in the cascadeindication subfield in all of the trigger frames are set to the samevalue (e.g., either all set to TRUE value or all set to FALSE value).

FIG. 4A is a diagram illustrating a format of a trigger frame, accordingto some embodiments. As shown, the trigger frame includes a framecontrol field, a duration field, a receiver address (RA) field, atransmitter address (TA) field, a common info field (or UL MU PPDUattributes field), multiple per-user info fields (or STA PSDU attributesfields), a padding field, and a frame check sequence (FCS) field. Thecommon info field is used to indicate various UL MU PPDU attributes.Each per-user info field is used to indicate various STA PSDU attributesfor a particular STA. The format of the trigger frame shown in thediagram is provided by way of example and not limitation. The commoninfo field can include more or less subfields than shown, and mayinclude different types of subfields.

FIG. 4B is a diagram illustrating a format of a common info field or ULMU PPDU attributes field, according to some embodiments. As illustratedin this example, the common info field includes a cascade indicationsubfield, persistent trigger subfield, a bandwidth subfield, a MU PPDUtype subfield, a guard interval (GI) subfield, a duration subfield, agroup identifier subfield, an access category (AC) subfield, an accesscategory restriction subfield, a padding subfield, a P matrix sizesubfield, and a cascade trigger info subfield. It should be understoodthat the format of the common info field shown in the diagram isprovided by way of example and not limitation. It should be understoodthat the common info field can include more or less subfields thanshown, and include different types of subfields. For example, the commoninfo field can include any of the subfields described above for a UL MUPPDU attributes field.

FIG. 4C is a diagram illustrating a format of a per-user info field orSTA PSDU attributes field, according to some embodiments. As illustratedin this example, the per-user info field includes a STA identifiersubfield, a new assignment identification subfield, an assignmentsubfield, a modulation coding scheme (MCS) subfield, a spatial streamsallocation subfield (which may include a number of spatial streamssubfield and a P matrix row subfield), and a padding subfield. It shouldbe understood that the format of the per-user info field shown in thediagram is provided by way of example and not limitation. It should beunderstood that the per-user info field can include more or lesssubfields than shown, and include different types of subfields. Forexample, the per-user info field can include any of the subfieldsdescribed above for a STA PSDU attributes field.

FIG. 5 is a flow diagram of a process implemented by a network devicefunctioning as an AP to initiate a UL MU simultaneous transmission,according to some embodiments. In one embodiment, the operations of theflow diagram may be performed by a network device functioning as an APin a wireless communications network (e.g., a WLAN). The operations inthis flow diagram and other flow diagrams will be described withreference to the exemplary embodiments of the other figures. However, itshould be understood that the operations of the flow diagrams can beperformed by embodiments other than those discussed with reference tothe other figures, and the embodiments discussed with reference to theseother figures can perform operations different than those discussed withreference to the flow diagrams.

In one embodiment, the process is initiated when the AP generates atrigger frame that initiates the UL MU simultaneous transmission, wherethe trigger frame includes a UL MU PPDU attributes field to indicateattributes pertaining to a UL MU PPDU transmitted to the AP during theUL MU simultaneous transmission that are common to a plurality of STAsthat are scheduled to participate in the UL MU simultaneous transmissionand a STA PSDU attributes field for a particular STA from the pluralityof STAs to indicate attributes pertaining to the UL MU PPDU that arespecific to the particular STA (block 510). In one embodiment, the UL MUPPDU attributes field includes one or more of the subfields describedabove for a UL MU PPDU attributes field. In one embodiment, the STA PSDUattributes field includes one or more of the subfields described abovefor a STA PSDU attributes field. Once the AP generates the triggerframe, the AP transmits the trigger frame through a wireless medium(block 520).

FIG. 6 is a flow diagram of a process implemented by a network devicefunctioning as a STA to participate in a UL MU simultaneous transmissionto an AP with one or more other STAs, according to some embodiments. Inone embodiment, the operations of the flow diagram may be performed by anetwork device functioning as a non-AP STA in a wireless communicationsnetwork (e.g., a WLAN).

In one embodiment, the process is initiated when the STA receives atrigger frame that initiates a UL MU simultaneous transmission from theAP, where the trigger frame includes a UL MU PPDU attributes field toindicate attributes pertaining to a UL MU PPDU transmitted to the APduring the UL MU simultaneous transmission that are common to the STAand one or more other STAs that are scheduled to participate in the ULMU simultaneous transmission and a STA PSDU attributes field for the STAto indicate attributes pertaining to the UL MU PPDU that are specific tothe STA (block 610). In one embodiment, the UL MU PPDU attributes fieldincludes one or more of the subfields described above for a UL MU PPDUattributes field. In one embodiment, the STA PSDU attributes fieldincludes one or more of the subfields described above for a STA PSDUattributes field. In response to receiving the trigger frame, the STAtransmits the UL MU PPDU (e.g., the STA's contribution to the UL MUPPDU) to the AP through a wireless medium during the UL MU simultaneoustransmission, according to one or more of the attributes pertaining tothe UL MU PPDU indicated in the UL MU PPDU attributes field and the STAPSDU attributes field for the STA (block 620). For example, in oneembodiment, the UL MU PPDU attributes field includes a guard intervalsubfield to indicate a guard interval that the STA and the one or moreother STAs are to apply to one or more portions of the UL MU PPDU. Inthis case, the STA may determine the guard interval that the STA is toapply to one or more portions of the UL MU PPDU based on an indicationin the guard interval subfield and apply the determined guard intervalto one or more portions of the UL MU PPDU. In one embodiment, the STAPSDU attributes field for the STA includes an assignment subfield toindicate a transmission resource unit that the STA is to use to transmita set of MPDUs within the UL MU PPDU to the AP during the UL MUsimultaneous transmission. In this case, the STA may determine thetransmission resource unit that the STA is to use to transmit the set ofMPDUs within the UL MU PPDU to the AP during the UL MU simultaneoustransmission and use the determined transmission resource unit totransmit the UL MU PPDU to the AP during the UL MU simultaneoustransmission. In one embodiment, the UL MU PPDU attributes fieldincludes a persistent trigger subfield to indicate whether one or moreof the attributes pertaining to the (upcoming) UL MU PPDU is the same asindicated in a previously transmitted trigger frame. In this case, theSTA may determine that one or more attributes pertaining to the(upcoming) UL MU PPDU is the same as indicated in the previouslytransmitted trigger frame based on an indication in the persistenttrigger subfield and apply one or more attributes indicated in thepreviously transmitted trigger frame to the (upcoming) UL MU PPDU. Inone embodiment, the UL MU PPDU attributes field includes a bandwidthsubfield to indicate a bandwidth of the UL MU PPDU. In this case, theSTA may determine the bandwidth of the UL MU PPDU based on an indicationin the bandwidth subfield and the transmission of the UL MU PPDU to theAP is based on the determined bandwidth of the UL MU PPDU. In oneembodiment, the UL MU PPDU attributes field includes a duration subfieldto indicate a length of the UL MU PPDU. In this case, the STA maydetermine the length of the UL MU PPDU based on an indication in theduration subfield and generate the UL MU PPDU such that the UL MU PPDUhas the determined length of the UL MU PPDU. In one embodiment, the ULMU PPDU attributes field includes an access category subfield toindicate an access category for data included in the UL MU PPDU. In thiscase, the STA may determine the access category for data included in theUL MU PPDU based on an indication in the access category subfield andprovide data in the UL MU PPDU that belongs to the access category. Inone embodiment, the STA PSDU attributes field for the STA includes anMCS subfield to indicate an MCS level that the STA is to use for one ormore portions of the UL MU PPDU. In this case, the STA may determine theMCS level that the STA is to use for one or more portions of the UL MUPPDU based on an indication in the MCS subfield and apply the determinedMCS level to one or more portions of the UL MU PPDU. In one embodiment,the STA PSDU attributes field for the STA includes a STA identifiersubfield to indicate an association identifier that identifies the STA.In this case, the STA may determine the association identifier based onan indication in the STA identifier subfield and determine that the STAPSDU attributes field for the STA indicates attributes pertaining to theUL MU PPDU that are specific to the STA based on a determination thatthe determined association identifier is an association identifierassociated with the STA. In one embodiment, the STA PSDU attributes forthe STA includes a spatial stream allocation subfield that includes anumber of spatial streams subfield to indicate a number of spatialstreams that the STA is to use to transmit the UL MU PPDU to the APduring the UL MU simultaneous transmission. In this case, the STA maydetermine the number of spatial streams that the STA is to sue totransmit the UL MU PPDU to the AP during the UL MU simultaneoustransmission based on an indication in the number of spatial streamssubfield and use the determined number of spatial streams whentransmitting the UL MU PPDU to the AP. In one embodiment, the spatialstreams allocation subfield also includes a P matrix rows subfield toindicate a set of rows of a P matrix that the STA is to use to generatea set of HE LTE symbols in the UL MU PPDU. In this case, the STA maydetermine the set of rows of the P matrix that the STA is to use togenerate a set of HE LTE symbols in the UL MU PPDU based on anindication in the P matrix rows subfield and generate a set of HE LTEsymbols in the UL MU PPDU based on the determined set of rows of the Pmatrix.

In one embodiment, the UL MU PPDU attributes field of the trigger frameincludes a cascade trigger info subfield, where the value in the cascadetrigger info subfield indicates the time at which the AP is expected totransmit the next trigger frame. The STA may determine the time at whichthe AP is expected to transmit the next trigger frame based on the valuein the cascade trigger info subfield (block 630).

The STA then transitions to a sleep or doze state (block 640) anddetermines whether the AP is expected to transmit the next trigger framesoon (e.g., based on the value in the cascade trigger info subfield)(decision block 650). If not, then the STA continues to wait until thetime at which the AP is expected to transmit the next trigger frame.However, if the STA determines that the AP is expected to transmit thenext trigger frame soon, then the STA transitions to an awake state(block 660) and receives the next trigger frame (block 670).

FIG. 7 is a block diagram of a network device implementing a STA or APthat executes a random access process and module, according to someembodiments. In a wireless local area network (WLAN) such as the exampleWLAN illustrated in FIG. 8 , a basic service set (BSS) includes aplurality of network devices referred to herein as WLAN devices. Each ofthe WLAN devices may include a medium access control (MAC) layer and aphysical (PHY) layer according to IEEE 802.11 standard. In the pluralityof WLAN devices, at least one WLAN device may be an AP station (e.g.,access point 0 and access point 1 in FIG. 8 ) and the other WLAN devicesmay be non-AP stations (non-AP STAs), (e.g., stations 0-3 in FIG. 8 ).Alternatively, all of the plurality of WLAN devices may be non-AP STAsin an Ad-hoc networking environment. In general, the AP STA and thenon-AP STA may be each referred to herein as a station (STA). However,for ease of description, only the non-AP STA will be referred to hereinas a STA whereas the AP stations are referred to herein as APs for easeof description. As shown in FIG. 8 , a WLAN can have any combination ofSTAs and APs that can form a discrete network, an ad hoc network or anycombination thereof. Any number of APs and STAs can be included in aWLAN and any topology and configuration of such APs and STAs in thenetwork can be utilized.

The example WLAN device 1 includes a baseband processor 10, a radiofrequency (RF) transceiver 20, an antenna unit 30, memory 40, an inputinterface unit 50, an output interface unit 60, and a bus 70. Thebaseband processor 10 performs baseband signal processing, and includesa MAC processor 11 and a PHY processor 15. These processors can be anytype of integrated circuit (IC) including a general processing unit oran application specific integrated circuit (ASIC). In some embodiments,the MAC processor 11 also implements a UL MU simultaneous transmissionmodule 700. The UL MU simultaneous transmission module 700 can implementthe respective functions for any combination of the embodimentsdescribed herein above with regard to FIGS. 1-5 . In other embodiments,the UL MU simultaneous transmission module 700 may be implemented by ordistributed over both the PHY processor 15 and the MAC processor 11. TheUL MU simultaneous transmission module 700 may be implemented assoftware or as hardware components of either the PHY processor 15 or MACprocessor 11.

In one embodiment, the MAC processor 11 may include a MAC softwareprocessing unit 12 and a MAC hardware processing unit 13. The memory 40may store software (hereinafter referred to as “MAC software”),including at least some functions of the MAC layer. The MAC softwareprocessing unit 12 executes the MAC software to implement some functionsof the MAC layer and the MAC hardware processing unit 13 may implementthe remaining functions of the MAC layer in hardware (hereinafterreferred to “MAC hardware”). However, the MAC processor 11 is notlimited to this distribution of functionality.

The PHY processor 15 includes a transmitting signal processing unit 100and a receiving signal processing unit 200 described further hereinbelow with reference to FIGS. 9 and 10 .

The baseband processor 10, the memory 40, the input interface unit 50,and the output interface unit 60 may communicate with each other via thebus 70. The radio frequency (RF) transceiver 20 includes an RFtransmitter 21 and an RF receiver 22. The memory 40 may further store anoperating system and applications. In some embodiments, the memory maystore recorded information about captured frames. The input interfaceunit 50 receives information from a user and the output interface unit60 outputs information to the user.

The antenna unit 30 includes one or more antennas. When a MIMO orMU-MIMO system is used, the antenna unit 30 may include a plurality ofantennas.

FIG. 9 is a schematic block diagram exemplifying a transmitting signalprocessor in a WLAN device, according to some embodiments. Referring tothe above drawing, a transmitting signal processing unit 100 includes anencoder 110, an interleaver 120, a mapper 130, an inverse Fouriertransformer (IFT) 140, and a guard interval (GI) inserter 150. Theencoder 110 encodes input data. For example, the encoder 110 may be aforward error correction (FEC) encoder. The FEC encoder may include abinary convolutional code (BCC) encoder followed by a puncturing deviceor may include a low-density parity-check (LDPC) encoder.

The transmitting signal processing unit 100 may further include ascrambler for scrambling the input data before encoding to reduce theprobability of long sequences of 0s or 1s. If BCC encoding is used inthe encoder 110, the transmitting signal processing unit 100 may furtherinclude an encoder parser for demultiplexing the scrambled bits among aplurality of BCC encoders. If LDPC encoding is used in the encoder 110,the transmitting signal processing unit 100 may not use the encoderparser.

The interleaver 120 interleaves the bits of each stream output from theencoder to change the order of bits. Interleaving may be applied onlywhen BCC encoding is used. The mapper 130 maps the sequence of bitsoutput from the interleaver to constellation points. If LDPC encoding isused in the encoder 110, the mapper 130 may further perform LDPC tonemapping in addition to constellation mapping.

When multiple input—multiple output (MIMO) or multiple user (MU)-MIMO isused, the transmitting signal processing unit 100 may use a plurality ofinterleavers 120 and a plurality of mappers 130 corresponding to thenumber N_(SS) of spatial streams. In this case, the transmitting signalprocessing unit 100 may further include a stream parser for dividingoutputs of the BCC encoders or the LDPC encoder into blocks that aresent to different interleavers 120 or mappers 130. The transmittingsignal processing unit 100 may further include a space-time block code(STBC) encoder for spreading the constellation points from the N_(SS)spatial streams into N_(STS) space-time streams and a spatial mapper formapping the space-time streams to transmit chains. The spatial mappermay use direct mapping, spatial expansion, or beamforming.

The IFT 140 converts a block of the constellation points output from themapper 130 or the spatial mapper to a time domain block (i.e., a symbol)by using an inverse discrete Fourier transform (IDFT) or an inverse fastFourier transform (IFFT). If the STBC encoder and the spatial mapper areused, the inverse Fourier transformer 140 may be provided for eachtransmit chain.

When MIMO or MU-MIMO is used, the transmitting signal processing unit100 may insert cyclic shift diversities (CSDs) to prevent unintentionalbeamforming. The CSD insertion may occur before or after the inverseFourier transform 140. The CSD may be specified per transmit chain ormay be specified per space-time stream. Alternatively, the CSD may beapplied as a part of the spatial mapper. When MU-MIMO is used, someblocks before the spatial mapper may be provided for each user.

The GI inserter 150 prepends a GI to the symbol. The transmitting signalprocessing unit 100 may optionally perform windowing to smooth edges ofeach symbol after inserting the GI. The RF transmitter 21 converts thesymbols into an RF signal and transmits the RF signal via the antennaunit 30. When MIMO or MU-MIMO is used, the GI inserter 150 and the RFtransmitter 21 may be provided for each transmit chain.

FIG. 10 is a schematic block diagram exemplifying a receiving signalprocessing unit in the WLAN, according to some embodiments. Referring toFIG. 10 , a receiving signal processing unit 200 includes a GI remover220, a Fourier transformer (FT) 230, a demapper 240, a deinterleaver250, and a decoder 260.

An RF receiver 22 receives an RF signal via the antenna unit 30 andconverts the RF signal into symbols. The GI remover 220 removes the GIfrom the symbol. When MIMO or MU-MIMO is used, the RF receiver 22 andthe GI remover 220 may be provided for each receive chain.

The FT 230 converts the symbol (i.e., the time domain block) into ablock of constellation points by using a discrete Fourier transform(DFT) or a fast Fourier transform (FFT). The Fourier transformer 230 maybe provided for each receive chain.

When MIMO or MU-MIMO is used, the receiving signal processing unit 200may use a spatial demapper for converting the Fourier transformedreceiver chains to constellation points of the space-time streams and anSTBC decoder for despreading the constellation points from thespace-time streams into the spatial streams.

The demapper 240 demaps the constellation points output from the Fouriertransformer 230 or the STBC decoder to bit streams. If LDPC encoding isused, the demapper 240 may further perform LDPC tone demapping beforeconstellation demapping. The deinterleaver 250 deinterleaves the bits ofeach stream output from the demapper 240. Deinterleaving may be appliedonly when BCC encoding is used.

When MIMO or MU-MIMO is used, the receiving signal processing unit 200may use a plurality of demappers 240 and a plurality of deinterleavers250 corresponding to the number of spatial streams. In this case, thereceiving signal processing unit 200 may further include a streamdeparser for combining the streams output from the deinterleavers 250.

The decoder 260 decodes the streams output from the deinterleaver 250 orthe stream deparser. For example, the decoder 260 may be an FEC decoder.The FEC decoder may include a BCC decoder or an LDPC decoder. Thereceiving signal processing unit 200 may further include a descramblerfor descrambling the decoded data. If BCC decoding is used in thedecoder 260, the receiving signal processing unit 200 may furtherinclude an encoder deparser for multiplexing the data decoded by aplurality of BCC decoders. If LDPC decoding is used in the decoder 260,the receiving signal processing unit 200 may not use the encoderdeparser.

FIG. 11 is a timing diagram providing an example of the Carrier SenseMultiple Access/Collision Avoidance (CSMA/CA) transmission procedure,according to some embodiments. In the illustrated example, STA1 is atransmit WLAN device for transmitting data, STA2 is a receive WLANdevice for receiving the data, and STA3 is a WLAN device, which may belocated at an area where a frame transmitted from the STA1 and/or aframe transmitted from the STA2 can be received by the WLAN device.

STA1 may determine whether the channel is busy by carrier sensing. TheSTA1 may determine the channel occupation based on a quality of thesignal on the channel or correlation of signals in the channel, or maydetermine the channel occupation by using a network allocation vector(NAV) timer.

When determining that the channel is not used by other devices duringDIFS (that is, the channel is idle), STA1 may transmit an RTS frame toSTA2 after performing backoff. Upon receiving the RTS frame, STA2 maytransmit a CTS frame as a response of the CTS frame after SIFS. WhenSTA3 receives the RTS frame, it may set the NAV timer for a transmissionduration of subsequently transmitted frames (for example, a duration ofSIFS+CTS frame duration+SIFS+data frame duration+SIFS+ACK frameduration) by using duration information included in the RTS frame. WhenSTA3 receives the CTS frame, it may set the NAV timer for a transmissionduration of subsequently transmitted frames (for example, a duration ofSIFS+data frame duration+SIFS+ACK frame duration) by using durationinformation included in the RTS frame. Upon receiving a new frame beforethe NAV timer expires, STA3 may update the NAV timer by using durationinformation included in the new frame. STA3 does not attempt to accessthe channel until the NAV timer expires.

When STA1 receives the CTS frame from the STA2, it may transmit a dataframe to the STA2 after SIFS elapses from a time when the CTS frame hasbeen completely received. Upon successfully receiving the data frame,the STA2 may transmit an ACK frame as a response of the data frame afterSIFS elapses.

When the NAV timer expires, STA3 may determine whether the channel isbusy through the use of carrier sensing techniques. Upon determiningthat the channel is not used by other devices during DIFS and after theNAV timer has expired, STA3 may attempt channel access after acontention window according to random backoff elapses.

The solutions provided herein have been described with reference to awireless LAN system; however, it should be understood that thesesolutions are also applicable to other network environments, such ascellular telecommunication networks, wired networks, and similarcommunication networks.

An embodiment may be an article of manufacture in which a non-transitorymachine-readable medium (such as microelectronic memory) has storedthereon instructions which program one or more data processingcomponents (generically referred to here as a “processor”) to performthe operations described above. In other embodiments, some of theseoperations might be performed by specific hardware components thatcontain hardwired logic (e.g., dedicated digital filter blocks and statemachines). Those operations might alternatively be performed by anycombination of programmed data processing components and fixed hardwiredcircuit components.

Some portions of the preceding detailed descriptions have been presentedin terms of algorithms and symbolic representations of operations ondata bits within a computer memory. These algorithmic descriptions andrepresentations are the ways used by those skilled in conferencingtechnology to most effectively convey the substance of their work toothers skilled in the art. An algorithm is here, and generally,conceived to be a self-consistent sequence of operations leading to adesired result. The operations are those requiring physicalmanipulations of physical quantities. It should be borne in mind,however, that all of these and similar terms are to be associated withthe appropriate physical quantities and are merely convenient labelsapplied to these quantities. Unless specifically stated otherwise asapparent from the above discussion, it is appreciated that throughoutthe description, discussions utilizing terms such as those set forth inthe claims below, refer to the action and processes of a conferencedevice, or similar electronic computing device, that manipulates andtransforms data represented as physical (electronic) quantities withinthe conference device's registers and memories into other data similarlyrepresented as physical quantities within the conference device'smemories or registers or other such information storage, transmission ordisplay devices.

While the flow diagrams in the figures herein show a particular order ofoperations performed by certain embodiments, it should be understoodthat such order is exemplary (e.g., alternative embodiments may performthe operations in a different order, combine certain operations, overlapcertain operations, etc.).

Those skilled in the art will recognize that the present disclosure isnot limited to the embodiments described, and that the techniquesdescribed herein can be practiced with modification and alterationwithin the spirit and scope of the appended claims. The description isthus to be regarded as illustrative instead of limiting.

What is claimed is:
 1. An Access Point (AP) operating in a WirelessLocal Area Network (WLAN), wherein the AP is to initiate an uplink (UL)multi-user (MU) simultaneous transmission, the access point comprising:a set of one or more processors; and a memory device, wherein the memorydevice stores instructions that when executed by the set of one or moreprocessors cause the AP to: generate a first trigger frame thatinitiates the UL MU simultaneous transmission, wherein the trigger frameincludes (1) a common attributes field to indicate attributes pertainingto a UL MU frame to be transmitted to the AP during the UL MUsimultaneous transmission that are common to a plurality of stations(STAs) that are to participate in the UL MU simultaneous transmissionand (2) a STA specific attributes field for a particular STA from theplurality of STAs that indicates attributes pertaining to the UL MUframe that are specific to the particular STA, wherein the commonattributes field includes a cascade trigger subfield to indicate whethera second trigger frame is scheduled to be transmitted following thefirst trigger frame and during a designated period, and transmit thefirst trigger frame through a wireless medium.
 2. The AP of claim 1,wherein a length of the cascade trigger subfield is one bit, wherein afirst state of the one bit indicates that the second trigger frame is tobe transmitted in the designated period, and wherein a second state ofthe one bit indicates that the second trigger frame is not to betransmitted in the designated period.
 3. The AP of claim 2, wherein whenthe cascade trigger subfield is set to the first state an additionalfield is to be used in the first trigger frame to assist in respondingto one or more of the first trigger frame and the second trigger frame,which allow for random access transmissions.
 4. The AP of claim 1,wherein the common attributes field further includes a bandwidthsubfield to indicate a bandwidth of the UL MU frame.
 5. The AP of claim1, wherein the common attributes field further includes a durationsubfield to indicate a length of the UL MU frame.
 6. The AP of claim 1,wherein the STA specific attributes field for the particular STAincludes a modulation and coding scheme (MCS) subfield to indicate anMCS level that the particular STA is to use for one or more portions ofthe UL MU frame.
 7. The AP of claim 1, wherein the STA specificattributes field for the particular STA further includes a STAidentifier subfield to indicate an association identifier thatidentifies the particular STA.
 8. The AP of claim 1, wherein the STAspecific attributes field further includes a number of spatial streamssubfield to indicate a number of spatial streams that the particular STAis to use to transmit the UL MU frame to the AP during the UL MUsimultaneous transmission, wherein the common attributes field furtherincludes a field that indicates information for generating a set of HighEfficiency (HE) Long Training Field (LTF) symbols in the UL MU frame. 9.The AP of claim 1, wherein a station that receives the first triggerframe determines whether to enter a doze state based on the cascadetrigger subfield.
 10. The AP of claim 1, wherein the trigger frameincludes a subfield that indicates a padding used for the UL MU frame.11. A station (STA) in a Wireless Local Area Network (WLAN), wherein theSTA is to participate in an uplink (UL) multi-user (MU) simultaneoustransmission in relation to an access point (AP) with one or more otherSTAs, the method comprising: a set of one or more processors; and amemory device, wherein the memory device stores instructions that whenexecuted by the set of one or more processors cause the STA to: receivea first trigger frame from the AP that initiates the UL MU simultaneoustransmission, wherein the trigger frame includes (1) a common attributesfield to indicate attributes pertaining to a first UL MU frametransmitted to the AP during the UL MU simultaneous transmission thatare common to the STA and the one or more other STAs and (2) a STAspecific attributes field for the STA that indicates attributespertaining to the first UL MU frame that are specific to the STA,wherein the common attributes field includes a cascade trigger subfieldto indicate whether a second trigger frame is scheduled to betransmitted following the first trigger frame and during a designatedperiod, determine whether the second trigger frame is scheduled to betransmitted following the first trigger frame and during the designatedperiod based on the cascade trigger subfield, and transmit the first ULMU frame to the AP through a wireless medium during the UL MUsimultaneous transmission based on the first trigger frame.
 12. The STAof claim 11, wherein a length of the cascade trigger subfield is onebit, and wherein a first state of the one bit indicates that the secondtrigger frame is to be transmitted in the designated period, and whereina second state of the one bit indicates that the second trigger frame isnot to be transmitted in the designated period.
 13. The STA of claim 12,wherein the instructions further cause the STA to: receive the secondtrigger frame from the AP; and transmit a second UL MU frame in responseto the second trigger frame based on the determination as to whether thesecond trigger frame is scheduled to be transmitted following the firsttrigger frame and during the designated period.
 14. The STA of claim 13,wherein when the cascade trigger subfield is set to the first state anadditional field is to be used in the first trigger frame to assist inresponding to the second trigger frame, which allow for random accesstransmissions.
 15. The STA of claim 14, wherein the transmission of thesecond UL MU frame is further based on the additional field of the firsttrigger frame when the cascade trigger subfield is set to the firststate.
 16. The method of claim 11, wherein the instructions furthercause the STA to: enter a doze state based on the cascade triggersubfield of the first trigger frame.
 17. The STA of claim 11, whereinthe common attributes field further includes a duration subfield toindicate a length of the first UL MU frame and a bandwidth subfield toindicate a bandwidth of the first UL MU frame, wherein the instructionsfurther cause the STA to: determine the length of the first UL MU framebased on an indication in the duration subfield, wherein the STAgenerates the first UL MU frame such that the first UL MU frame has thedetermined length; and determine the bandwidth of the first UL MU framebased on an indication in the bandwidth subfield, wherein the STAtransmits the first UL MU frame to the AP based on the determinedbandwidth of the first UL MU frame.
 18. The STA of claim 11, wherein theSTA specific attributes field for the STA includes (1) a STA identifiersubfield to indicate an association identifier and (2) a modulation andcoding scheme (MCS) subfield to indicate an MCS level that the STA is touse for one or more portions of the first UL MU frame, wherein theinstructions further cause the STA to: determine that the STA specificattributes field for the STA indicates attributes pertaining to thefirst UL MU frame that are specific to the STA based on a determinationthat the association identifier is an association identifier associatedwith the STA; and determine the MCS for the one or more portions of thefirst UL MU frame based on an indication in the MCS subfield.
 19. TheSTA of claim 18, wherein the association identifier indicates that theSTA specific attributes field is associated with random accesstransmissions.
 20. The STA of claim 11, wherein the STA specificattributes field further includes a spatial streams (SS) allocationsubfield that indicates a number of spatial streams that the STA is touse to transmit the first UL MU frame to the AP during the UL MUsimultaneous transmission and the common attributes field furtherincludes a Long Training Field (LTF) subfield that indicates informationfor generating a set of High Efficiency (HE) LTF symbols in the first ULMU frame, wherein the instructions further cause the STA to: determinethe number of spatial streams that the STA is to use to transmit thefirst UL MU frame to the AP during the UL MU simultaneous transmissionbased on an indication in the number of spatial streams subfield,wherein the STA transmits the first UL MU frame to the AP using thedetermined number of spatial streams; and generate the set of HE LTEsymbols in the first UL MU frame based on the LTF subfield.